Sonic process of placement of sand drains



Jan. 7, 1969 A. G. BODINE, JR

SONIC PROCESS OF PLACEMENT OF SAND DRAINS 2 f O a m \M. Q 3 w 3 m m F INVENTOR. jigs/ 2 Gjodzlzafi I IE V m wa aw xk J I 9 U 7 0\ 0 0 m E w. J

Jan. 7, 1969 A. G. BODINE, JR

SONIC PROCESS OF PLACEMENT OF SAND DRAINS Filed Feb. 10, 1966 Sheet 2 of2 v y wv v M n M. v A

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United States Patent 3,420,063 SONIC PROCESS OF PLACEMENT 0F SAND DRAlNS Albert G. Bodine, Jr., Los Angeles, Calif. (7877 Woodley Ave., Van Nuys, Calif. 91406) Filed Feb. 10, 1966, Ser. No. 526,542

US. CI. 61-11 3 Claims Int. Cl. E02b 11/00 ABSTRACT OF THE DISCLOSURE A method of installing water drainage sand pillars in the ground comprising inserting a tubular casing of elastic material into the ground, filling the casing with sand, and elastically vibrating the casing While simultaneously withdrawing it from the ground, leaving the sand pillar therein.

The present invention is based upon the concept of first installing a hollow casing in the ground, then filling this casing with sand or similar granular material, and thereafter sonically activating the casing so that the latter can be removed, leaving a pillar of sand installed in the earth. The sonic activation comprises in its preferred form a longitudinal resonant standing wave set up in the casing, such that the sand column inside the casing is sonically agitated and thus maintained and finally deposited in a desirable loose or uncornpacted condition, while still completely filling the hole left by the extracted casing.

The principal present application of this process, though not necessarily the only one, is in the reclaiming of swampy or water-laden soils. Thus, there are many land areas which remain undeveloped solely because of poor soil stability owing to large water content. These soil types commonly exist around the perirneters of cities, as along river banks and in marshes. The city develops around these areas because they can not be put to good use. They are not suitable for supporting structures such as buildings or roads. This potentially valuable land can be reclaimed if sufliciently economical techniques are made available for extracting the moisture therefrom,

so that the soil becomes rigid and stable for the purpose of normal usages.

Attempts have been made to reclaim such marshy land by installing vertical pillars of sand in the body of waterladen soil. These sand pillars function something like a blotter, extracting the water from the surrounding body of Wet soil. The water oozes from the upper ends of the pillars, and is conveyed away. This result may be accomplished over an area by installing a suitable number of pillars, usually with close spacing. The sand drains alforded thereby function somewhat like well holes in reverse. Instead of entering the well hole, water enters into the interstices between sand grains, while the physical structure of the pillar of sand grains holds the more finely divided soil particles, commonly silt, against material intrusion into the sand pillar.

In aid of this progress, after installation of the sand pillars, a surcharge of weight is then placed on top of the moisture-laden ground, usually by hauling in foreign soil from some distant region. This surcharge of weight causes the soil to experience a pressure which then increases the flow of water toward and into the sand pillars. Under these conditions, water oozes out of the top of the sand drains. It can be conducted away by ditches, though I prefer for this purpose a horizontal layer of sand in stalled between the original water-laden ground surface and the soil overburden mentioned hereinabove. After a 3,420,063 Patented Jan. 7, 1969 time, the entire area is reclaimed by virtue of the fact that the water has been extracted from the original overly moist and sometimes even soupy soil, so that the result is a composite mass of very stable soil which consists, first, of the initially water-laden soil which has been drained by the sand pillars, together with the overburden of added soil on top, which then becomes the initial or top surface on which buildings, roads, etc., may be built.

One of the main problems in this procedure is the provision of an inexpensive and rapid system for installing the vertical sand pillars in the water-laden and often quite soupy soil. Very often this is a considerable problem. By conventional techniques known heretofore, the sand pillars are installed using a hammer-type pile driver, driving a casing into the ground, and then the casing is filled with sand. The remaining large problem is then that when the casing is subsequently extracted, the sand, which has often become quite impacted, does not drain rapidly out the bottom of the casing so as to form immediately a full-diameter sand pillar capable of holding back the wet soil around the outside of the casing as the casing is extracted. Thus, in the conventional process, the extraction of the casing is often accompanied by sand tending to stick within the casing, and not falling immediately and freely out of the bottom thereof, or with suflicient rapidity as to prevent the mushy wet soil from closing in underneath the casing, and thus intruding into the space intended for the sand pillar, whereby the formation of a good sand pillar capable of carrying out its intended function is prevented. In other words, one of the problems is that the sand often tends to hang up inside the casing sometimes even coming out of the ground along with the casing, with the inevitable production of a deficient sand pillar.

A general object of the invention is accordingly the provision of an improved technique by which such sand pillars may be installed with substantially improved efliciency and effectiveness, and with substantially improved assurance that the pillars will be installed in fullbodied form, as intended, .such as will efficiently and effectively carry out the water drainage function for which they are intended.

Considered briefly, the present invention improves upon prior practices first of all by. initial instalment of the easing by sonic pile driving techniques, as more particularly referred to presently. The next and most important phase is then that this casing, after being filled with sand, can be extracted by pulling upwardly on it While vibrating it as by setting up therein a pattern of resonant, sonic, standing wave vibration, such standing wave vibration is characterized by elastic vibrations of the substance of the casing in the region of resonance, whereby the sand with in the casing is maintained in an active and agitated condition so that it flows out of the casing as the casing is elevated with complete freedom, almost like water, Thus the sand comes out so fast that it rapidly fills the void immediately under the lower edge of the casing as the casing rises, and therefore the surrounding Wet soil does not have the time or opportunity to intrude into the space intended for the sand pillar. The main result, then, by use of the sonic process is that a very full-bodied, effective sand pillar, of desired cross-sectional area, can be effectively installed in water-laden ground.

Of course, in addition to the improvement made in the structure of the sand pillar are the additional benefits gained from sonic driving of the casing, and by sonic extraction of the casing after the sand has been put in, both of which operations are far more expeditious and economical than techniques heretobefore employed. The economics of installation of the sand drains are thus great- 1y improved by the sonic techniques of the present invention.

Described in more detail, the practice of this invention involves first the installation of the casing, which can be done by first drilling a hole for the casing (provided that the soil is firm enough for so doing), or by sonically driving the casing into the ground in a manner disclosed in my Patent No. 2,975,846 dealing with the subject of sonic pile driving. The casing may have a loose cap on the bottom end, or it may have a self-dumping check valve mounted on the bottom thereof, so that in either case, when the casing is extracted from the ground, the bottom end is left open. After installation of the casing in the ground, with the bottom end thus closed, the casing may be filled with the sand or other equivalent granular material as above noted.

Then as the sonic casing is sonically activated and extracted from the ground, the bottom dump mechanism, whether it be a separable cap, or some type of dump valve, opens so that the column of sand spills freely from the sonically activated casing and thus fills the hole formerly occupied by the casing to virtually the full diameter of the latter, so that a full-diameter sand pillar, without intrusion of the wet surrounding soil, is attained.

The sand in the sand pillar formed by the present process stands in a very desirably loose and porous condition during and following sonic extraction of the casing. Apparently, an acoustic circuit phenomenon occurs which tends towards preservation of the sand in this loose, freerunning condition. In this connection, the casing, which is an elastic member, along with a vibration generator coupled thereto, behaves when vibrated at the proper resonant frequency for standing wave vibration, as a discrete acoustic circuit, with the load on the circuit consisting substantially exclusively of the frictional loading afforded by the sand inside it, and the mud or water-laden soil outside. Thus, in this resonant performance, the casing supplies both the mass and elastic compliance reactances, which equalize and cancel one another when vibration is at a certain frequency known as the resonant frequency of the circuit. Under these conditions, the sand inside the casing is caused to vibrate by contact with the casing, but portions of the contained sand, or the entire body thereof, for that matter, do not supply either mass or elastic compliance reactances so as to enter into the resonant performance. The mass and/or elastic compliance factors of the sand thus do not become factors in the acoustic circuit performance. The friction afforded by the sand, of course, is directly coupled to the acoustic circuit comprised of the casing, and thus constitutes a resistive load thereon. Under these conditions, established in the operation of the invention, regions or bodies of the contained sand do not vibrate in unison so as to bring about a resonant performance through participation of such a body of sand in a unitary type of vibration. In this connection, it should be explained that in certain types of pile driving systems, for example, wherein a pile may be vibrated in engagement with the earth at a low-order frequency which does not set up a resonant standing wave vibration in the pile itself, the pile can sometimes go into a kind of resonant performance with a localized body of the penetrated soil, which latter sometimes tends to vibrate bodily with the pile, and so supply either or both the necessary mass and elastic compliance reactances necessary to this type of resonant performance. However, as has been amply demonstrated in pile driving practice such as disclosed in my heretofore mentioned Patent No. 2,975,846, a much more effective pile driving action is attained by going to the higher order of frequency ranges such as are capable of setting up standing wave vibration patterns in the pile itself, with surrounding soil then prevented from participating in the resonant phenomenon, and so acting merely as a resistive load on the acoustic circuit. This same advantage is availed of in the present invention, but to the gain of a considerably different benefit, in that by avoidance of large regions or bodies of sand vibrating in unison to supply a resonant function, the grains of sand, acting merely as resistive impedances, vibrate only randomly as regards both amplitude and direction. Compaction is thus avoided, and the sand remains extremely loose and fluid as the sonic performance proceeds. The unique result then obtains that the sand pillar stands in the earth like a body of liquid as the casing is moved up and out of the hole, the sand then standing in place of and completely filling the space formerly occupied by the casing. This follows, since there is in this system no tendency for the sand to be pulled up out of the ground as the casing itself is extracted. Thus, the sand fully filling the hole as the casing ascends, any cave-in of the side walls of the hole is prevented, and the installation of a full-bodied column of sand or sand pillar is made possible.

It will be seen that the fluidizing effect within the sand by the kind of sonic performance utilized in the invention causes the sand to quickly flow out of the bottom end of the casing and to run out instantaneously into intimate contact immediately at the bottom edge of the casing, as the casing rises, and thus this intimate and immediate contact of the sand completely fills the space against the walls of the water-laden earth material as the casing is extracted. Cave-in of, or intrusion by, the surrounding earth material as the casing is extracted is thus effectively prevented.

An additional important advantage of the system is that the sonic action within the sand consisting of random vibration thereof results in the sand within the sand pillar being left in a loose and uncompacted condition so as to have maximum porosity for the surrounding water, though the sand pillar structure is still effective as a barrier against intrusion of the surrounding soil.

Among the unique advantages of the invention are the ability to install very long sand drains or pillars, and to install these in very soft and soggy soils, such as in extreme conditions of marsh land. The invention is uniquely effective in muddy soils which have no stability. The sonic action causes the sand to quickly fill out as the casing is extracted, thus holding back even extremely wet or muddy soils and preventing their intrusion into the sand. The invention permits the economic de-watering and reclamation of soils which otherwise have no value.

An additional step in accordance with the invention is to apply to a layer of overburden soil placed over the initial water-laden soil, a sonic compacting action, using for example a sonic compactor of the type disclosed in my Patent No. 2,897,734. Such application of a sonic compactor machine causes increased compaction of the soil surrounding the sand drains, so as to enhance the compacting effect of the overburden layer. On the other hand, the sand pillars, having been installed under conditions of sonic activation, remain readily responsive to sonic action, and thus compact less in response to the action of the sonic compactor than does the surrounding normal heterogeneous silt or the like of the original but now largely dried out swamp soil.

In this regard it will be appreciated that the original water-laden soil normally includes a large proportion of very fine grained material, and it will be evident that the sonic action applied to the soil is particularly effective in causing compaction when there is a substantial range of particle sizes, with inclusion of fined grained material, such as occurs in many normal soils. On the other hand, by using uniformly coarse grained sand, or the like, for the sand pillars, increased rather than decreased porosity tends to follow sonic vibration, because there are no fine particles to work their way in 'between the vibrating large particles. The final result is thus a compacted soil region, in which are installed vertical sand pillars of virtually permanent water porosity, such that moisture can be constantly drained from the soil on a long term basis, assuring soil stability and safety of structures installed there;

on. In some cases, of course, when the soil has been once dried out and reclaimed, and the source of moisture shut off, further drainage will not be necessary, and the sand pillars can be abandoned.

Sonic discussion Certain acoustic phenomena. disclosed in the foregoing and hereinafter, are, generally speaking, outside the experience of those skilled in the acoustics art. To aid in a full understanding of these phenomena by those skilled in the acoustics art, and by others, the following general discussion, including definition of terms, is deemed to be of importance.

By the expression sonic vibration I mean elastic vibrations, i.e. cyclic elastic deformations, which travel through a medium with a characteristic velocity of propagation. If these vibrations travel longitudinally, or create a longitudinal wave pattern in a medium or structure having uniformly distributed constants of elasticity of modulus, and mass, this is sound wave transmission. Regardless of the vibratory frequency of such sound wave transmission, the same mathematical formulae apply, and the science is called sonics. In addition, there can 'be elastically vibratory systems wherein the essential features of mass appear as a localized influence or parameter, known as a lumped constant; and another such lumped constant can be a localized or concentrated elastically de formable element, affording a local effect referred to variously as elasticity, modulus, modulus of elasticity, stiffness, stiffness modulus, or compliance, which is the reciprocal of the stiffness modulus. Fortunately, these constants, when functioning in an elastically vibratory system such as mine, have cooperating and mutually influencing effects like equivalent factors in alternating-current electrical systems. In fact, in both distributed and lumped constant systems, mass is mathematically equivalent to inductance (a coil); elastic compliance is mathematically equivalent to capacitance (a condensor); and friction or other pure energy dissipation is mathematically equivalent to resistance (a resistor).

Because of these equivalents, my elastic vibratory systems with their mass and stiffness and energy consumption, and their sonic energy transmission properties, can be viewed as equivalent electrical circuits, where the functions can be expressed, considered, changed and quantitatively analyzed by using well proven electrical formulae.

It is important to recognize that the transmission of sonic energy into the interface or work area between two parts to be moved against one another requires the above mentioned elastic vibration phenomena in order to accomplish the benefits of my invention. There have been other proposals involving exclusively simple bodily vibration of some part. However, these latter do not result in the benefits of my sonic or elastically vibratory action.

Since sonic or elastic vibration results in the mass and elastic compliance elements of the system taking on these special properties akin to the parameters of inductance and capacitance in alternating current phenomena, wholly new performances can be made to take place in the mechanical arts. The concept of .acoustic impedance becomes of paramount importance in understanding performances. Here impedance is the ratio of cyclic force or pressure acting in the media to resulting cyclic velocity or motion, just like the ratio of voltage to current. In this sonic adaptation impedance is also equal to media density times the speed of propagation of the elastic vibration.

In this invention impedance is important to the accomplishment of desired ends, such as where there is an interface. A sonic vibration transmitted across an interface between-two media or two structures can experience some reflection, depending upon differences of impedance. This can cause large relative motion, if desired, at the interface.

Impedance is also important to consider if optimized energization of a system is desired. If the impedances are adjusted to be matched somewhat, energy transmission is made very effective.

Sonic energy at fairly high frequency can have energy effects on molecular or crystalline systems. Also, these fairly high frequencies can result in very high periodic accelenation values, typically of the order of hundreds or thousands of times the acceleration of gravity. This is because mathematically acceleration varies with the square of frequency. Accordingly, by taking advantage of this square function, I can accomplish very high forces with my sonic systems. My sonic systems preferably accomplish such high forces, and high total energy, by using a type of sonic vibration generator taught in my Patent No. 2,960,314, which is a simple mechanical device. The use of this type of sonic vibration generator in the sonic system of the present invention affords an especially simple, reliable, and commercially feasible system.

An additional important feature of these sonic circuits is the fact that they can be made very active, so as to handle substantial power, by providing a high Q factor. Here this factor Q is the ratio of energy stored to energy dissipated per cycle. In other words, with :a high Q factor, the sonic system can store a high level of sonic energy, to which a constant input and output of energy is respectively added and substracted. Circuit-wise, this Q factor is numerically the ratio of inductive reactance to resistance. Moreover, a high Q system is dynamically active, giving considerable cyclic motion where such motion is needed.

Certain definitions should now be given:

Impedance, in an elastically vibratory system, is, mathematically, the complex quotient of applied alternating force and linear velocity. It is analogous to electrical impedance. The concise mathematical expression for this impedance is where M is vibratory mass, C is elastic compliance (the reciprocal of stiffness, or of modulus of elasticity) and f is the vibration frequency.

Resistance is the real part R of the impedance, and represents energy dissipation, as by friction.

Reactance is the imaginary part of the impedance, and is the difference of mass reactance and compliance reactance.

Mass reactance is the positive imaginary part of the impedance, given by 21rfM. It is analogous to electrical inductive reactance, just as mass is analogous to inductance.

Elastic compliance reactance is the negative imaginary part of impedance, given by Elastic compliance reactance is analogous to electrical capacitative reactance, just as compliance is analogous to capacitance.

Resonance in the vibratory circuit is obtained at the operating frequency at which the reactance (the algebraic sum of mass and compliance reactances) becomes zero. Vibration amplitude is limited under this condition to resistance alone, and is maximized. The inertia of the mass elements necessary to be vibrated does not under this condition consume any of the driving force.

A valuable feature of my sonic circuit is the provision of enough elastic compliance reactance so that the mass or inertia of various necessary bodies in the system does not cause the system to depart so far from resonance that a large proportion of the driving force is consumed and wasted in vibrating this mass. For example, a mechanical oscillator or vibration generator of the type normally used in my inventions always has a body, or carrying structure, for containing the cyclic force generating means. This supporting structure, even when minimal, still has mass, or inertia. This inertia could be a force-wasting detriment,

acting as a blocking impedance using up part of the periodic force output just to accelerate and decelerate this supporting structure. However, by use of elastically vibratory structure in the system, the effect of this mass, or the mass reactance resulting therefrom, is counteracted at the frequency for resonance; and when a resonant acoustic circuit is thus used, with adequate capacitance (elastic compliance reactance), these blocking impedances are tuned out of existence, at resonance, and the periodic force generating means can thus deliver its full impulse to the work," which is the resistive component of the impedance.

Sometimes it is especially beneficial to couple the sonic oscillator at a low-impedance (high-velocity vibration) region, for optimum power input, and then have high impedance (high-force vibration) at the work point. The sonic circuit is then functioning additionally as a transformer, or acoustic lever, to optimize the effectiveness of both the oscillator region and the Work delivering region.

For very high impedance systems having high Q at high frequency, I sometimes prefer that the resonant elastic system be a bar of solid material such as steel. For lower frequency or lower impedance, especially where large amplitude vibration is desired, I use a fluid resonator. One desirable specie of my invention employs, as the source of sonic power, a sonic resonant system comprising an elastic member in combination with an orbiting mass oscillator or vibration generator, as above mentioned. This combination has many unique and desirable features. For example, this orbiting mass oscillator has the ability to adjust its input power and phase to the resonant system so as to accommodate changes in the work load, including changes in either or both the reactive impedance and the resistive impedance. This is a very desirable feature in that the oscillator hangs on to the load even as the load changes.

It is important to note that this unique advantage of the orbiting mass oscillator accrues from the combination thereof with the acoustic resonant circuit, so as to comprise a complete acoustic system. In other words, the orbiting mass oscillator is matched up to the resonant part of its system, and the combined system is matched up to the acoustic load, or the job to be accomplished. One manifestation of this proper matching is a characteristic whereby the orbiting mass oscillator tends to lock in to the resonant frequency of the resonant part of the system.

The combined system has a unique performance which is exhibited in the form of a greater effectiveness and particularly greater persistence in a sustained sonic action as the work process proceeds or goes through phases and changes of conditions. The orbiting mass ocsillator, in this matched-up arrangement, is able to hang on to the load :and continue to develop power as the sonic energy absorbing environment changes with the variations in sonic energy absorption by the load. The orbiting mass oscillator automatically changes its phase angle, and therefore its power factor, with these changes in the resistive impedance of the load.

A further important characteristic which tends to make the orbiting mass oscillator hang on to the load and continue the development of effective power, is that it also accommodates for changes in the reactive impedance of the acoustic environment while the work process continues. For example, if the load tends to add either inductance or capacitance to the sonic system, then the orbiting mass oscillator will accommodate accordingly. Very often this is accommodated by an automatic shift in frequency of operation of the orbiting mass oscillator by virtue of an automatic feedback of torque to the energy source which drives the orbiting mass oscillator. In other words, if the reactive impedance of the load changes this automatically causes a shift in the resonant response of the resonant circuit portion of the complete sonic system. This in turn causes 8 a shift in the frequency of the orbiting mass oscillator for a given torque load provided by the power source which drives the orbiting mass oscillator.

All of the above mentioned characteristics of the orbiting mass oscillator are provided to a unique degree by this oscillator in combination with the resonant circuit. As explained elsewhere in this discussion the kinds of acoustic environment presented to the sonic source by this invention are uniquely accommodated by the combination of the orbiting mass oscillator and the resonant system. As will be noted, this invention involves the application of sonic power which brings forth some special problems unique to this invention, which problems are primarily a matter of delivering effective sonic energy to the particular work process involved in this invention. The work process, as explained elsewhere herein, presents a special combination of resistive and reactive impedances. These circuit values must be properly met in order that the invention be practiced effectively.

The invention will be further understood by referring to the following detailed description of illustrative equipment for carrying the invention into effect, reference for this purpose being had to the accompanying drawings, in which:

FIG. 1 is a longitudinal vertical section through a casing, a vibrator for driving the same into the earth, the casing being shown after installation in the earth;

FIG. 2 is a view taken in accordance with line 22 of FIG. 1;

FIG. 3 is a section taken on line 33 of FIG. 1

FIG. 4 is a vertical section through a lower end portion of a modified casing, showing a type of dump valve;

FIG. 5 is a modification of FIG. 4; and

FIG. 6 illustrates the use of a compactor machine for sonic compaction of the earth material around a plurality of installed sand pillars.

In FIG. 1, there is illustrated at 10 a body of soil which is understood to be of a swampy or water-laden nature, often of a mushy or soupy consistency, but in any event containing such a proportion of water as requires drainage in order that the soil can be put to use. Numeral 11 designates generally an elastic casing, composed, for example, of an elastic material such as steel, and which has been installed in soil 10. In some cases, a well casing may be employed, or a tubular metal pile. The casing will be understood to have been installed by inserting it in a previously dug hole, if this has been possible, or preferably by sonic driving as in my Patent No. 2,975,846. In FIG. 1, the bottom end of this casing 11 is shown to be closed by a removable closure 12. It will be understood that this closure 12 fits frictionally, though with sufiicient looseness that it can be easily forced out in a subsequent step of the operation, inside the bottom end of the casing. Coupled to the upper extremity of the casing 11 is a vibration generator generally designated by the numeral 13, described in more particular hereinafter, and which is designed to apply to the casing 11 cyclic force impulses in vertical direction at a frequency such as to establish in the casing longitudinal, resonant, standing wave vibration. It should be here mentioned that while a feature of the invention is the creation of a resonant standing wave in the casing 11, this standing wave need not be of the longitudinal type, as a torsional standing wave, for example, but also be provided, or even a lateral wave, in some cases, but the longitudinal type wave is preferred, and provisions for this type of wave are here illustrated, though without necessary implication of limitation thereto. As recited in complete detail in my aforesaid Patent No. 2,975,846, a resonant standing wave of a longitudinal pattern can be set up in the casing 11 by coupling to one end thereof a vibration or cyclic force generator such as the generator 13 already mentioned. This generator exerts an alternating force longitudinally on the upper extremity of the casing. By proper relation of the frequency of this alternating force to the length of the casing, according to the relationship where f is the fundamental resonant frequency, s is the velocity of sound in the material of the casing, and h is the length of the casing, a half-wavelength standing waveis set up in the casing, with velocity antinodes V at the two extremities of the casing, and a velocity node N at the approximate mid-point. The velocity antinodes will be understood to be regions of maximized vibration amplitude, and the node N to be a region of minimized vibration amplitude. In this type of longitudinal standing wave performance, the two half lengths of the casing elastically elongate in step with and in opposition to one another, with the amplitude of elastic vibration increasing progressively from the mid-point to each of the two ends.

The vibration generator 13 in the form here shown for illustrative purposes is preferably of an orbital mass type, referred to in the introductory portion of the specification. In this intsance, the generator 13 is in two parts 13a and 13b secured rigidly against opposite sides of the upper end portion of casing 11 by bolts 14. It will be understood that these parts 130! and 13b coact through the upper end of casing 11 so as to act as a unitary wave generator. This type of wave generator and its operation are disclosed in more particular in my prior Patent No. 2,960,314. Each of members 13a and 13b comprises a housing embodying a cylindrical wall 15 forming a cylindrical raceway 16. Two side plates 17 engage opposite edges of each circular side wall 15, and form with wall 15 a cylindrical chamber in which is confined a generally cylindrical inertia rotor 18. The rotor 18 is of a diameter substantially smaller than that of the raceway 16, and is adapted to roll therearound in an orbital path, exerting a centrifugal force on the wall 15. The rotor 18 is driven in this fashion by a jet of air, steam or other fluid, under pressure introduced tangentially of the raceway via a nozzle bore 19 supplied by pressure hose 20. Spent air escapes via ports 21 inside plates 17.

It will be seen from the drawings that the two inertia rotors are driven in opposite directions of rotation. The two rotors 18 are automatically phased by the pile resonance to run in synchronism with one another. That is to say, they are always at corresponding points of their respective orbital paths. Thus they move up and down together, and, by virtue of their opposite directions of orbital motion, they move laterally in opposition to one another. Accordingly, the vertical components of the force exerted by the rotors on the generator housings, and thence on the casing 11, are in phase and additive; while the horizontal force components are equal and opposite and cancel. The fluid pressure driving the rotors is made such that the number of circuits per second taken by the rotors around their raceways is in the range of the resonant frequency of the casing 11 for a mode of longitudinal standing wave vibration of the mandrel, usually the half-wavelength mode. Assuming the halfwavelength mode, a standing wave is characterized by the two half-length portions of the mandrel alternately elastically elongating and contracting 'with the mid-point of the casing experiencing a velocity mode or pseudonode of the standing wave, i.e. having minimum vibration amplitude, and the two end portions experiencing velocity antinodes, i.e. vibrating in directions longitudinal of the rod at maximum amplitude.

At first, the two rotors 18 have random phase relations. Very shortly, they chance to come into such phase relations as to cooperate, or be additive, to a degree in vertical motion (longitudinally of the casing). When that occurs, a component of vertically oscillating force is exerted on the generator housing, and therefore on the upper end of casing 11, and if the frequency is in the range of fundamental resonance, the casing will vibrate, possibly only feebly at first, in an approximation to the desired half-wave standing wave mode. Once this process is started, the resonantly vibrating casing, cooperating with properly matched rotor force, tends to vibrate at a frequency just under peak resonance frequency for the casing; and this controlled vibration of the matched casing back-reacts on the rotors to hold them both at the frequency of vibration of the casing, and to bring them into synchronism with each other. As they synchronize, the amplitude of the standing wave increases to maximum.

Casing 11 is tightly fitted near its upper end with an external piston 22, which works in an air cylinder 23, having a bottom wall 24 slidably surrounding and pressure sealed, as at, 25, to the casing. The piston 22 is airsealed to cylinder 23 as at 26. The cylinder space 27 below piston 22 is supplied with air under pressure via an air hose 28. The air pressure maintained in space 27 is sufilcient to act as an air spring for support of the casing 11 and generator 13.

Cylinder 23 has a pair of eyes 30 suspended through links 31 from the arms of a hanger 32, hung, in turn, by means of a cable 33, from any suitable lowering and hoisting gear such as is conventionally used in connection with derricks, cranes, etc., not shown.

At 35 is illustrated a chute leading from a fragmentarily illustrated hopper 36, the latter being understood to be supported from above by equipment capable of maneuvering it into position such that the chute 35 discharges into the upper end of casing 11 when the casing is in the driven position of FIG. 1.

Operation is as follows: As heretofore mentioned, it is possible with some soils to introduce or install the casing 11 to the position of FIG. 1 by first forming a bore hole of the proper diameter and then simply sliding the casing 11 down into it. Preferably, however, the casing is driven into the ground by using sonic pile driving procedures disclosed in my aforementioned Patent No. 2,975,846. In this process, the vibration generator 13 is operated at a frequency equal to the fundamental resonant frequency of the casing 11 for its longitudinal resonant standing wave vibration performance, as described hereinabove. Also, the casing is biased downwardly by mass loading arising out of the weight of the generator components 13a and 13b clamped thereto, and by additional added mass if necessary in any given instance. The lower end of the casing is first engaged with the surface of the ground, the closure 12 being in place. Tension in the support cable 33 is then relaxed to permit imposition of the bias force on the ground surface at the lower end of the casing. Under these conditions, the soil underneath the casing becomes fluidized, if it is not already virtually a fluid, and thus accepts intrusion of the casing, which moves fairly rapidly down into the soil.

The casing may thus be driven to such a position as illustrated in FIG. 1. Loose sand, or the equivalent, preferably relatively coarse and of fairly uniform grain size, is then introduced into the casing via the chute 35, which has been maneuvered into position. The casing is thus filled up to or preferably somewhat above the level of ground surface 10, sonic vibration being of course at this stage suspended.

The -most critically important step is now to extract the casing, and to fill the space left thereby by the sand in the casing, using vibrating activity in the casing to keep the sand agitated and loose, and assure its continuous and completely free fall or spill from the lower end of the casing as the casing is elevated. Thereby, there is assurance that the sand fills in the full diameter of the space formerly occupied by the casing, running instantly under the lower edge of the casing as the casing rises, so that there is no opportunity for intrusion of the immediately surrounding moisture-laden and often mushy or fluid earth material.

The preferred and most effective form of vibration is resonant standing wave vibration, and while various modes of standing wave vibration are available, the simplest and best practice is considered to involve the use of resonant longitudinal standing wave vibration in the casing while the casing is being elevated. Elevation is accomplished by exerting an upward tension in the suspension cable 33, in coaction with the described vibration in the casing, and under these conditions, particularly with use of a longitudinal resonant standing wave in the casing, the casing moves up easily and rapidly with tension exerted on the suspension cable 33. Of course, as the casing rises, the closure or plug 12 initially in the bottom of the casing is held down by the column of sand above it. Thus the spill of sand out the lower end of the casing begins instantly that the casing separates slightly from the closure 12. This continues as the casing is pulled out of the ground, and under the conditions described, a full-bodied cylinder of loose sand, such as indicated at 50 in FIG. 6, is installed in the surrounding moistureladen soil. This occurs without material intrusion of the surrounding soil into the pillars, or with only such minor intrusion as can be neglected.

In FIG. 6, adjacent sand pillars are shown as having been covered over and interconnected by a horizontal layer of sand 51 which has been placed over the surface of the initial soil 10. This layer of sand 51, which may be a number of inches thick, can be supplied or at least contributed to by excess sand placed in the easings 11, and dumped therefrom when the casings are finally lifted from the ground surface. Additional sand may then be added to build up the layer 51; or, if the initial sand pillars are built up only to a level of the initial soil level 10, the entire layer 51 can be added subsequently.

The layer of sand 51, whose function will be referred to presently, may be regarded as an optional feature of the invention, but one which is preferred, at least for many typical installations.

A final layer 52, this time of soil, is then placed as a top overburden, either directly on the surface of the soil 10, if the sand layer 51 is not used, or if the sand layer 51 is used, then over the latter, as illustrated in FIG. 6.

The sand layer 51 and the soil overburden 52 will be seen to exert a downward pressure on the soil 10. A certain compaction of the soil is thereby achieved. The sand pillars 50, however, having been deposited to the accompaniment of sonic agitation, and particular- 1y when the sand particles are largely of uniform size, do not compress and compact to the same extent, partly by reason of having been formed initally under conditions of sonic agitation, and partly because of absence of finely divided particles capable of entering into the spaces between larger particles. The sand pillars 50 thus remain somewhat open and porous for easy flow of water therethrough. Pressure on the soil 10, on the other hand, is such as to cause water therein to enter into the spaces between the sand particles of the pillars 50, so that the latter then become filled with water. This water must then be drained away from the upper ends of the sand pillars, and to this end, ditches may be constructed, as in older practice. I have here shown, however, my preferred use of the horizontally disposed sand layer 51 as a means of carrying off water conducted thereto by the sand pillars 50. Thus, it will be seen that moisture from the initial soil material 10 enters into the sand pillars 50, fills the latter and so rises to suitably constructed ditches, or, in the alternative, to the installed sand layer 51, through which it flows off laterally to any suitably constructed sump or disposition facility.

In FIG. 6 I have also shown a sonically vibratory machine "for additionally compacting the soil structure, and thus accelerating the process. Illustrated in FIG. 6 is a preferred form of sonic compacting machine as disclosed in my prior Patent No. 2,897,734, and reference to said patent may be had for a complete understanding. For present purposes, it will suffice to point out that the sonic compacting machine is a wheeled vehicle 60 carrying a frame structure 61 from which is suspended a large and heavy earth-engageable block 62, with a vibration generator 63 mounted thereon. The vibration generator may be driven from a prime mover 64. With the block 62 in engagement with the surface of the soil layer 52, and the vibration generator 63 in operation, the block 62 radiates sonic compressional waves of corresponding frequency down into the composite soil structure below. This operation compacts the composite soil structure below, and thus squeezes water therefrom; but it does not equally compact the sand pillars 50, laid down under conditions of sonic agitation. These tend to remain loose, particularly under the sonic agitation resulting from the operation of the sonic compacting machine. Thus, additional compaction and pressure is exerted on the soil 10, resulting in accelerated and increased moisture flow laterally to and into the pillars 56', while at the same time, the pillars 50 are not subject to corresponding compaction. This is particularly true if the sand particles have been laid down under conditions of sonic agitation, and also if the sand particles are of largely uniform size. Thus, by this additional procedure, the flow of water from the soil 10 into the sand pillars, and thence up the sand pillars to the drainage layer 51, or ditches, as the case may be, is materially accelerated.

The over-all process permits the economic reclamation of many potentially valuable marsh lands and the like, which now stand useless because of the expense of heretofore known water drainage operations.

In FIGS. 4 and 5 I have shown two alternative constructions for the lower end of the casing, to be used in lieu of the closure plug 12 of FIG. 1. In FIG. 4, the casing, here designated at 11a, and which may in this case be of square cross-section, is formed at the bottom with two hinged doors 70, which are placed initially in closed position, and may be provided with stops, not shown, to hold them against COllapsing upwardly. These doors will obviously open downwardly when the casing 11a is lifted while full of sand.

In FIG. 5 is shown a casing 11b, with a single closure plate 71 pivoted off-center of the axis of casing. The larger side of this closure plate 71 engages under the edge of the casing 11b in the closed position, and thus remains closed while the casing is driven downwardly into the soil. As the casing is subsequently elevated, however, the loading on the large side of the plate 71 will exceed that on the smaller side thereof, so that the plate 71 necessarily swings open and permits free discharge of the contained sand.

It will of course be understood that the present drawings and description are for illustrative purposes only, and that various changes in design, structure and arrangement of the equipment, as well as modifications in the method of procedure, may be made without departing from the spirit and scope of the invention or of the appended claims.

-I claim 1. The process of installing a water drainage sand pillar in water-laden ground, that comprises:

installing a tubular casing of elastic material in the medium of the ground, with the upper end thereof near ground level;

filling said casing substantially to ground level with sand;

setting up elastic vibration in the form of a resonant sonic standing wave in and longitudinally of said casing; and

exerting an upward withdrawal force on said casing during said elastic vibration thereof, so as to withdraw said casing from the ground, while the sand 13 14 in the casing spills from the lower end thereof and References Cited g s g g p l g S m 8 nd s UNITED STATES PATENTS s1 care 1 8.111 6 n sai a 1n a1 caslngt into sonic agitation and thereby causing it to spill freely and continuously from the lower end of said 5 casing as the casing is elevated, whereby to aid the filling of the space formerly occupied by the casing 2,897,734 8/1959 Bodine. 2,975,846 3/1961 Bodine.

as the casing is raised and thereby to reduce in- 3187513 6/1965 i 61-53] X trusion of water-laden ground media into said space. 3256695 6/1966 Bodms 61-725 X 2, The subject matter of claim 1, using a casing 3282055 11/1966 Lansiau 6111X equipped at the bottom end with a closure which opens 10 3303656 2/1967 Landau 61 11 X when the casing is elevated while filled with sand. OTHER REFERENCES 3. The subject matter of claim 1, including initially Roads and Streets: p. 99; September 1955; (copy in installing said casing in the ground by setting up elastic vibration therein while exerting a steady downward bias 15 force thereon. EARL J. WITMER, Primary Examiner.

group 355, class 61, subclass 11). 

